People have said they were banned for only rotations.
I was not banned (3 accounts), but not sure why. I went ahead and closed my subs for now as I do not feel it is safe at the moment, and was pretty bored anyway.
I don't think anyone knows the detection method, but this is what I did in the time from 6.0 to banwave:
-I never used the HB launcher, and closed HB prior to closing WoW.
-I used rotations with movement off, enyo, and sometimes fishingbuddy.
-I quested by hand using rotations and zygors guide. (I have used questing bots quite a bit, but not after 6.1/WoD, other than a test which looked too bottish)
-I was active in world chat, worldpvp etc
-I did not use garrisionbot, pvp bots, battlepet bots, etc. I did use rotations in ashran.
-I turned off interrupts in the rotations
-I didn't really use the auction house, except for rare purchases.
-I was online for the big tripwire event that happened shortly before the banwave.
No idea if any of these contributed to my not getting banned. I have not played wow without HB in years.